Phonograph tone arm



vMlllr 691953 w. BLlNoFF :TAL 2,833,867

l PHoNoGRAPH Tous ARM med sept. 11, 1953 2 sheets-sheet 1 MIY 6 1958 w. BLlNoFF ETAL 2,833,867

PHoNoGRAPH Tous: ARM mea spt. 11, 1195s United States Patent O PHNOGRAPH TONE ARM` William Blinoii, Prospect Heights, Lester C. Gutschick and Joseph E. Wrzepski, Chicago, and Fred P. Venditti, Lisle, Ill., assignors to Motorola, Inc., Chicago, lll., a corporation of Illinois Application September 11, 1953, SealNo. 379,518

4 Claims. v(Cl. 179-100.41)

The present invention relates to an improved and simplified tone arm for use withl a phonograph, radiophonograph combination, or the like.

It is an object of the present inventionv to provide an improved tone arm for a phonograph or the like that is inexpensive and extremely simple in its construction, and which is exceedingly light in weight to reduce record wear to a minimum.

Another object of the invention is to provide such an improved tone arm in which the pick-up cartridge is readily removable for replacement purposes.

Still another object of the invention is to provide such an improved. tone arm in which the moving mass therein isl reduced to a minimum to achieve, high fidelity sensitivity through a wide range of frequencies.

A still further object of the invention isA to provide such an improved tone arm that is constructed so that dust or other particles on a record associated therewith have no appreciable ei'ect on the tonal qualitiesof the device.

A further object of the invention is, to provide such an improved tone arm that` is extremely ruggedv in its construction andV in which. the electrical components thereof are adequately shielded fromelectrostatic interference.

A feature of the invention is the provision of an improved phonograph tone arm composed ofa lightweight channel which is preferably metallic for electrostatic shielding purposes, with a pair of leads. extending along the channel` and connected to a pair of'resilient contacts mounted on a receptacle block supported inthe channel; and a removable pick-up cartridge supported in a presstit at one extremity of the channel and having a pair of electrically conductive members protruding therefrom and plugged into the respective resilient. contacts in the receptacle.

Another feature ofthe invention is the. provision of such an improved tone arm in which the pick-up cartridge comprises a molded plastic block having -an internal cavity with a movable electrically conductive vane supported within the cavity in variable capacitive relation with the end of a stud threaded through the. block, these simple elements cooperating to provide the desired operating characteristics for the device.

Yet another feature of the invention is the provision of such an improved and simplified tone arm in which electrical connection is conveniently made to the aforementioned stud by means of a metallic rod extending through the plastic block and traversingthe stud in electrical connection therewith, with the rod protruding through the block and extending alonggthe tone arm into one of the resilient contacts in the receptacleV referred` to above.

A still further featureofthe invention is the provision of such an improved tone armV in which electrical connection is conveniently made to the aforementioned'movable vane in the cavity of the plastic block bymeans ot an: electrically conductive member integral with the vane i direction normal to the plane of 2,833,867 Patented May 6, 1.958

flce.

and protruding through the block into the other resilient contact of the receptacle, the. electrically conductive member also serving to support the Vane and allowing resilient motion thereof perpendicular to the end of the stud referred to above. f

Another feature of the inventionis the provisionA of such an improved tone ,arm in whichf-a stylus. is formed integrally with the free end of the vane so as. to protrude from the plastic block, the stylus -being shapedj so that vibration thereof due to record grooves engaged by the stylus causes the vane to vibrate with respect. to the end of the stud, but. any motion thereof perpendicular to such vibration is absorbed and is not transmittedto the vane. so that foreign particles in the grooves ofthe record do not alfect the tonal qualities of the device.

The above and other features of the invention which are believed to be new are set forth with particularity in the appended claims. The invention itself, however, together with further objects andv advantages thereof, may best be understood by reference to the following description when taken in conjunction with the accompanying drawings in which:

Figure 1 is a top perspective view of the improved tone arm of the invention; Y y y Figure 2 is a bottom view of an end portionv of the tone arm;

Figure 3 is a perspective `view of the picloupcartridge portion of the tone arm ofthe invention;

Figure 4 is a side sectional view, greatly enlarged for purposes of clarity, of the above-mentionedend portion of the ,tone arm to show details of the pick-.up cartridge;

Figure 5 is a cross-sectional view of the tone arm la component of the tone arm.

vThe invention provides a phonograph tone arm which comprises a lightweight channel and a molded bloclc of insulating material having an internal cavity. A molded plastic front piece is affixed to the block and the front piece engages an extremity of the channel ina press fit to supportV the block within the channel'. An electrical conductive vane is supported in the cavity in the block by an electrically conductive integral supporting member which extends through the block and resiliently holds the vane in the cavity, allowing the vane to be vibrated in a direction normal to its plane. A stylus andcoupler are formed integral with the free end of the vane and the stylus protrudes beyond the bloclgthe coupler being formed so that vibratory movement of the stylus in a the vane vcauses the vane to vibrate in that directionabout its supportingy member. A stud. member is threaded through the block along an axis essentially perpendicular to the plane of the vane with the end of the stud. spaced from the vane to form a capacitive element therewith. An electrically conductive member is mounted in the block and traverses the stud in electrical contact therewithgand this conductive member, together with the supporting member for the vane, protrudes through the block, and. extends along the channel into disengageable electrical" contact with a'receptacle supported in thechannel.

Referring now to Figures l, 2V and 3 the improved tone arm of the present invention illustratedtherein includes a channel 10 that may be made, for example, of a plastic, a lightweight metal, or other suitable material.-4 lt has been found advantageous for channel 1t) to be .cornposed of a lightweightrnetal` such as aluminum t0; elieluded" therein While retaining the lightweight character- .istics of the arm. The channel is fabricated by molding, casting, forming or the like, to have the illustrated configuration and it is pivoted at one end to the phonograph associated therewith. The forward portion of the channel may be surrounded by a strip 10a of a 'brilliant metal such as brass for decorative purposes, the

strip being atlxed in any suitable manner to the outer surface of the channel.

The tone arm also includes a pick-up catridge which comprises a two-piece housing including a pair of insulating molded plastic blocks 13 and 14 which are held together by a metal clamp 12 surrounding the blocks. The blocks 13 and 14, alternately, can be held together by cementing or other means when so desired. The

blocks 13 and 14 have an insulating molded plastic end piece 16 which is'cemented or otherwise aixed thereto,

'and the end piece is forced into a press-tit with the exceptacle block 17 includes a pair of resilient metallic con- 'tacts 20 and 21 which releasably receive a pair of projecting electrical conductive members from the pick-up cartridge which members are to be described more fully hereinafter. Contacts 20 and 21 have respective connecting lugs 20a and 21a extending through the block 17, and shielded leads 22, 23 are electrically connected by soldering or the like to the respective lugs. The outer shield 24 of leads 22, 23 is coupled to the channel 10 (which is grounded) through a pair of ground plates 2S and 26, the ground plates being electrically and mechanically coupled to the channel. Leads 22 and 23 extend rearwardly through the channel and are electrically connected to the phonograph circuit with which the tone arm is associated.

' .The pick-up cartridge, therefore, is supported in an extremely simple manner within channel 10 and electrically connected to leads 22, 23 through receptacle 17.

When it is desired to replace the cartridge, it may be removed from the channel by withdrawing its end piece 16 from the extremity of the channel and simultaneously disengaging its conductive members from the resilient contacts 20 and 21 Vofreceptacle 17.

Reference is now made to Figures 4, 5 and 6 which show details of the improved pick-up cartridge of the tone arm of the invention. The blocks 13 and 14 dene an internal cavity 24 and a metallic electrically conductive vane 25 is supported within the cavity by an elongated electrically conductive supporting member 26. The supporting member 26 is formed integral with the upper end of the vane. The supporting member is flattened in the plane of the vane and extends between blocks 13 and 14 at an angle to the longitudinal axis of the vane and is rigidly maintained between the blocks. The supporting member 26, therefore, allows the vane to vibrate resiliently in a direction substantially perpendicular to the plane of the vane about the axis of the supporting member. The supporting member protrudes through blocks 13 and 14 and extends into one of the resilient contacts 20 and 21 of receptacle 17 of Figure 2.

VA stylus and coupler 27are formed integral at the other end of vane 25, the coupler serving to connect the stylus to the vane. The stylus protrudes through the bottom of blocks 13 and 14 to engage the grooves of a record 28, such as shown in Figure l. The stylus has a tip of sapphire, osmium, or other suitable extremely hard material. The stylus and coupler are formed in a manner to be described so thatlateral movement of the stylusby the grooves of record 28 causes vane 2.5 to vibrate about the electrically conductive supporting member 26, but any motion of the stylus normal to such lateral motion is absorbed by the compliance of the coupler and is not translated to the vane. A resilient cushion 29 may be mounted on an integral projection from block 13 within cavity 24 adjacent vane 25 for damping purposes if so desired.

An electrically conductive threaded stud 30 is threaded through block 14 and has a longitudinal axis substantally perpendicular to the plane of vane 25. The stud has an'essentially flat end 31 substantially parallel to the vane and is adjustably spaced therefrom so that the vane and the stud form a variable capacitive element. In this manner, stud 30 may be adjusted to form the desired initial capacity of the cartridge by threading the stud into block 14 until it has a desired position as measured by a micrometer. Therefore, vibration of the vane about the axis of its integral supporting member varies the capacity between the vane and the stud; and when the stylus engages the groovesof a record 28, such capacity variations are in accordance with the recordings on the record. An electrically conductive member 32 is supported in block 14 and extends across the threaded stud 30 in electrical contact therewith. Member 32 protrudes through block 14 and extends back along channel 10 parallel to member 26 into the other resilient contact of receptacle block 17. Therefore, by means of members 26 and 32, contacts 19 and 20, and leads 22 and 23, the capacity variations between stud 30 and vane 25 are incorporated into the electrical circuit of the phonograph.

The stylus and coupler 27, vane 25 and supporting member 26 may expeditiously be formed from a single resilient wire or rod in the manner lshown in Figure 7. This resilient rod is shown in Figure 7a and may, for example, `have a diameter of 27 mils and a length of about 1%", and the rod is provided with a hardtip composed, for example, of sapphire or osmium, or other suitable material. The vane 25 and supporting member `26 are formed by bending the rod of Figure 7a at the junction of these sections and swaging these sections of the rod fiat as shown in Figure 7b. The width of vane 18 may, for example, be .070"-.0O74". The stylus and coupler portion 27 is then formed by swaging the remaining section of the rod at in a plane perpendicular to vane 25 as shown in Figure 7c. After flattening, the stylus and coupler portion is usually sheared to a width of .O25"-.030. As av final step in the process, the coupler is bent to the desired configuration as shown in Figure 7d. The coupler of the resulting assembly, therefore, is in the form of .a strip lying in a plane essentially perpendicular to the plane of vane 25 so that the coupler has little cornpliance when the stylus is'moved laterally by the record grooves in a direction normal to the plane of vane 2S. Therefore, the stylus, in following the record grooves, causes vane 25 to vibrate in accordance with the recorded information. However, the coupler has a large compliance to motion of the stylus in a direction parallel to the plane of vane 25 and any motion in this latter direction, therefore, is absorbed by the coupler and is not transmitted to the vane. Due to this latter compliance of the coupler, any dust or other extraneous matter in the record grooves is absorbed by the coupler and the reproduction of the phonograph is unaffected thereby.

vWhen so desired, stylus and coupler 27 may be formed by swaging it llat in the same plane as vane 2S and supporting member 26, and then imparting a twist to the coupler, and then bending it into the shape shown iniFigure 4 so that it has the desired configuration to transmit lateral vibration to vane 25 and to absorb motion perpendicular to such lateral vibration.

The present invention provides, therefore, an improved tone arm that is extremely simple and economical in its construction since it involves relatively few and simple component parts. Moreover, the parts .of the tone arm ofwthehinvention; can lallAbe constructed of lightweight materials so as to reduce the mass of the tone arm and thereby reduce record wear. The pick-up cartridge of the device is held in the arm in a press-fit with its electrical contacts releasably plugged into a receptacle, and this facilitates the ease with which the cartridge may be removed for replacement purposes. The vane and the stylus constitute a moving mass of negligible weight so that the stylus is capable of following the most minute record grooves with the vane responding thereto so as to provide the wide range of frequencies to which the device is sensitive and thereby achieve high fidelity reproduction by an inexpensive assembly. The vertical compliance of the coupler renders the tone arm insensitive to dust or other particles in the record grooves so that the tonal qualities of the reproduction are unimpaired thereby, When the channel is composed of a lightweight metal, such as aluminum, this results in an extremely rugged arm with an adequate electrostatic shield for the electrical components therein.

While a particular embodiment of the invention has been shown and described, modifications may be made and it is intended in the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

We claim:

l. A phonograph pick-up cartridge including in combination, housing means having a cavity therein, an electrically conductive vane, an electrical conductive member integral with one end of said vane and supported in said housing means for resiliently supporting said vane in said cavity, a stylus formed integral with the other end of said vane and extending through said cavity and without said housing means, and an electrically conductive stud mounted in said housing means with its longitudinal axis substantially perpendicular to the plane of said vane and having an end within said cavity and spaced from said vane to constitute a variable capacitive element therewith, said stud being adjustable along the longitudinal axis thereof to vary the spacing between said end and said vane.

2. A phonograph pick-up cartridge including in combination, insulated housing means having a cavity therein, an electrically conductive vane, a first electrically conductive member integral with one end of said vaneand supported by said housing means with said vane in said cavity for resilient vibration about said conductive member in a direction substantially perpendicular to the plane of said vane, a stylus formed integral with the other end of said vane and extending outside of said cavity, an electrically conductive stud mounted in said housing means with its longitudinal axis substantially perpendicular to the plane of said vane and having an end thereof extending into said cavity and spaced from said vane to constitute a variable capacitive element therewith, and a second electrically conductive member supported by said housing means in electrical contact with said stud, said first and second electrical conductive members protruding from said housing means to provide respective electrical contacts to said vane and stud.

6 3. A phonograph pick-up cartridge including in combination, two-piece molded plastic housing means delining an internal cavity with an open side, an electrically conductive vane, a lirst electrically conductive member integral with one end of said vane and supported between the two pieces of said housing means for supporting said vane in said cavity for resilient vibration about said conductive member in a direction substantially perpendicular to the plane of said vane, a stylus formed integral with the other end of said vane and extending through said open side, an electrically conductive stud mounted in said housing means and extending through one of the pieces thereof with its longitudinal axis substantially perpendicular to the plane of said vane and having an end spaced from said vane to constitute a variable capacitive element therewith, and a second electrically conductive member supported in said housing means in electrical contact with said stud, said rst and second electrically conductive members protruding through said housing means to provide respective electrical contacts for said vane and stud.

4. A phonograph pick-up cartridge including in combination, housing means having a cavity therein, an electrically conductive vane, a iirst electrically conductive member integral with one end of said vane and disposed at an obtuse angle with respect thereto, said rst electrically conductive member being substantially at in the plane of said vane and supported in said housing means for supporting said vane in said cavity for resilient vibration about said conductive member ina direction substantially perpendicular to the plane of said vane, a stylus for-medintegral with the other end of said vane and extending outside of said housing means, an electrically conductive threaded stud mounted in said housing means and extending through one of the pieces thereof with its longitudinal axis substantially perpendicular to the plane of said vane and having an end spaced from said vane to constitute a variable capacitive element therewith, said stud being adjustable along the longitudinal axis thereof to vary its spacing from said vane, and a second electrically conductive member supported in said housing means and extending across said threaded stud in electrical contact therewith, said first and second electrically conductive members protruding through said housing means to provide respective electrical contacts for said vane and stud.

References Cited in the tile of this patent UNITED STATES PATENTS 1,909,995 Yeider May 23, 1933 2,322,621 Farrow June 22, 1943 2,426,061 Snepvangers Aug. 19, 1947 2,432,444 Roberts Dec. 9, 1947 2,478,234 Cain Aug. 9, 1949 2,556,040 Miller et al June 5, 1951 2,676,807 Goldmark Apr. 27, 1954 

